1. Field
The present disclosure relates generally to communication systems, and more particularly, to enabling fast handover for access technologies that utilize narrow, link-specific antenna beam pairs.
2. Background
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
Wireless access technologies in the millimeter wave (mmW) range require narrow, path-specific antenna beams (e.g., pencil beams) to be communicated between end points to overcome high propagation loss and reduced multipath diversity. Due to a short wavelength and limited link margin in the millimeter wave, a wireless channel becomes sensitive to shadowing effects. Such shadowing effects may be mitigated via macro diversity. For example, a mobile terminal currently being served by a serving base station may handover to an alternative target base station when the link to the serving base station becomes impaired. Current mobility protocols, e.g., protocols defined by 3GPP or Internet Engineering Task Force (IETF), are generally too slow to follow fast shadowing effects. Moreover, according to the current mobility protocols, every handover operation in which the mobile terminal participates requires a training sequence to be conducted between the mobile terminal and the target base station to create a matching pencil beam pair, which adds to an overall handover delay. Accordingly, what is needed is a solution that enables fast handover for access technologies that utilize narrow, link-specific antenna beam pairs.